1. Field of the Invention
The present invention relates to an image capture device with a zoom lens provided to a device body through a zoom mechanism.
2. Description of Related Art
In a conventionally used image capture device with a zoom lens (hereinafter referred to as a zoom-type image capture device), the zoom lens is provided to a device body through a zoom mechanism. The zoom mechanism includes a lens barrel to which the zoom lens is fixed, and a motor for causing the lens barrel to move back and forth along the optical axis of the zoom lens. An operational button for operating the zoom mechanism is provided to the device body of the zoom-type image capture device. Pressing the operational button supplies power to the motor to cause the motor to rotate, thereby causing the lens barrel of the zoom mechanism to move back and forth along the optical axis. As a result, the zoom lens moves back and forth along its optical axis, so that a captured image is zoomed in or out.
The motor includes a photointerrupter provided to part of the shaft or the transmission mechanism of the motor, and which can count the number of optical pulses determined by the amount of rotation of the motor. The counted number supplied from the photointerrupter is given to a controller incorporated in the zoom-type image capture device. The controller knows the position of the zoom lens based on the counted number acquired from the photointerrupter.
Now, it is assumed that external force acts on the zoom mechanism when power supply to the motor stops. In this case, the motor is caused to rotate by the action of the external force even though power supply to the motor stops, by which the lens barrel of the zoom mechanism may disadvantageously move along the optical axis. If power supply to the photointerrupter also stops at this time, the photointerrupter cannot count the number of optical pulses determined by the amount the motor rotated as a result of the action of the external force. This falls short of reaching a counted number required for the controller to know the precise position of the zoom lens. As a result, the actual position of the zoom lens deviates from the position of the zoom lens the controller knows.
The above-described zoom-type image capture device performs focusing based on a counted number acquired from the photointerrupter. So, shortage in a counted number due to failing to incorporate the amount the motor rotated as a result of the action of external force results in incorrect focus. Besides, the zoom lens may go out of its originally supposed movable region, by which the zoom-type image capture device may be mechanically damaged.
In response, it has been suggested that power be supplied to the photointerrupter even when power supply to the motor stops. In this structure, even when the lens barrel of the zoom mechanism is caused to move along the optical axis by the action of external force to cause the motor to rotate, the photointerrupter can count the number of optical pulses determined by the amount the motor rotated as a result of the action of the external force. So, the controller can know the precise position of the zoom lens.
In the conventionally used image capture device, however, the photointerrupter should be in a ready state to count the number of optical pulses determined by the amount of rotation of the motor when the zoom-type image capture device is ON, meaning that the photointerrupter always consumes power. This reduces the number of images that can be captured without requiring change of a battery (dry cell battery or rechargeable battery) in the zoom-type image capture device.